Asked Questions at the CSO
1. What is
submillimeter? What is submillimeter astronomy?
word ‘submillimeter’ refers to the wavelength of electromagnetic wave
detected by this telescope. The size range of the wavelength is
one millimeter (approximately 1/25 inch) and longer than 100 micron
(1/250 inch). The submillimeter region of the
spectrum is at the border between the far infrared and the
short-wavelength radio regions. As such, it borrows technologies from
both regimes: bolometers
from the infrared, heterodyne
the radio. Water vapor in the Earth’s atmosphere strongly absorbs
these radiations so that submillimeter telescopes need to be located at
places such as on high mountains or on the Antarctic plateau (for
example, AST/RO is a
submillimeter telescope at South Pole). The
transparency of the atmosphere to submillimeter radiation is shown here.
Note that the wavelength 1mm corresponds to 300 GHz and 300 micron
corresponds to 1000 GHz (1 THz), respectively. At Mauna Kea,
precipitable water vapor (sometimes called PWV) under good observing
is less than 1 mm.
The ability to detect such submillimeter waves have been developed only
in recent decades. This, combined with
the need for a high-altitude site, has resulted in submillimeter
astronomy being among one of the newest and least studied areas of
astronomy. Submillimeter radiations are generated in very cold,
dusty regions of space, which are the targets of broad astronomy
fields, such as star formation, interstellar medium, planetary systems,
evolved stars, evolution of galaxies, and cosmology. Astronomers
have special interest
in this wavelength, and many important studies remain to be done.
2. When was the
The CSO 10.4m telescope was completed and started operation at
top of Mauna Kea in 1986.
3. Who built the
CSO 10.4m telescope was designed and assembled by a team led by Dr.
Since radio astronomers built the telescope system,
including the instruments and software, the CSO is one of the easiest
telescopes to use for astronomical observations. It is
note that there are no telescope operators at the observatory,
because observers know enough to run the telescope to take
their scientific data (one has to have some technical
background to operate the telescope). Many key
instruments are developed by
graduate students and staff members at the observatory. Major
funding for the CSO is provided by the
4. How many staff
members work at the CSO?
Compared with other observatories at the mountain Mauna Kea, the CSO
group is relatively small. As of June 2005, 11 staff members and
one volunteer are
working at Hilo, about 13 staff members working at Caltech Pasadena
campus. The director of the observatory is Dr. Tom
Phillips, professor at the Physics
Department (part of the
Division of Physics Mathematics, and Astronomy(PMA)), California Institute
5. Can I look through
The CSO Leighton telescope does not have anything that anyone will look
through. This is a radio telescope, so the observing wavelength of this
telescope is much longer than optical
wavelengths (see also FAQ #1 written above). The human eye
is not sensitive at this wavelength. Instead, we have very
detectors including submillimeter/millimeter cameras (for
observations) and heterodyne
receivers (for spectroscopic observations). One can take long
integrations (exposures) using these
instruments. The ability of integrating over long
period allows astronomers to detect very faint objects that are
difficult to be detected. The data acquired by the instruments
will be stored on a computer and be analyzed in detail after
observations are completed (read also FAQ #8).
If you wish to explore the magnificent views of the beautiful night sky
from Mauna Kea area, you may go to the Onizuka Center for
International Astronomy Visitor Information Station (VIS), located
mid level of the mountain. They will provide you many kinds of
telescopes which you
can look through to explore the universe.
6. Can you observe in
day-time as well as night-time?
As it is a radio telescope, one can observe at any time during
night or day with the CSO
telescope. However, typical observing operation occurs starting in
the evening at about 7pm and ceases at about 7am.
When the observing weather is extremely good, observations are
extended into daytime. Daytime operations are restricted by Sun
avoidance as we must keep direct Sunlight off of the collecting surface
for safety reasons. Other factors restricting daytime
astronomical use of the telescope include our need to service
instruments, mechanical running gear, and so forth.
7. Who uses the
The observatory is owned and operated by Caltech under a contract from the National Science Foundation.
About one third of the time at the CSO Leighton telescope is reserved
for Caltech (including JPL) users. One half of the time is for national and
international observers, and the remainder is for users from the University of Hawai'i and the University of Texas at Austin.
Specific projects will be selected by Telescope Allocation Committees
called TAC) at each institution,
which meet twice a year, after two proposal semesters in May and
October. Astronomers apply to their
local TAC, which decides if a proposal is scientifically feasible and
has an impact in the fields. The observing proposals submitted to
the TACs will be ranked and a scheduler will allocate time
according to the priorities and
coordinates of targets. If weather is not good
enough on the assigned nights, one has to apply for telescope
An important feature of the CSO is that it can provide a platform for
new instruments being developed by some of our
users. For example, in recent years, the CSO has been hosting
instruments being developed by researchers at Cardiff
University, JPL(Jet Propulsion
of Colorado, University
of Western Ontario, and so on.
8. How often do
astronomers use the telescope?
Some projects require a lot of
observing time, others require just a couple of nights. On
average, astronomers use the telescope only a few nights a
year. Astronomers spend a long time (typically weeks or months) to
prepare their observing
includes determining the priority and making backup plans for
unpredictable weather. Once the data
been obtained, a great deal of time will be spent on analysis. It
often takes months or even years
to turn the raw data into scientific results. Astronomers spend
most of their time on this analysis, researching others' work,
collaborators to fit results into a big picture, and describing the
results in papers to publish.
9. Do you have open
Unfortunately no. However, we join many local events in Hilo,
such as Astroday, Onizuka Science Day,
Journey through the
Universe (Hilo HI) Family Science day,
and so on.
10. Do you have more
explanations on your technical terms/acronyms
written on your web pages?
For example, you may try to look for the terms or words in Astronomy
compiled by NED (NASA/IPAC
Extragalactic Database, at Caltech). ('Glossary' means a list of
technical or special words, explaining their meanings. ) You can find
quite a lot of
which provide you astronomy/physics glossary, through search engine web
sites such as Google.
Go back to A
Digest of Recent News and
Scientific Results at the Caltech Submillimeter Observatory